The present exemplary embodiment relates to an apparatus and method for introducing a refining agent into molten metal. It finds particular application in conjunction with a system for introducing a predetermined amount of chloride flux into a trough of molten aluminum, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Molten metals such as aluminum are known to include high levels of oxide and/or nitride debris that have a negative effect on the solidification of the particular alloy. The melted or liquefied form of aluminum also attracts the formation and absorption of hydrogen within the molten aluminum. Hydrogen evolves as porosity during the solidification of aluminum alloys and is detrimental to the mechanical properties of the solid alloy. Degassing is an effective way of reducing hydrogen caused porosity.
One example of degassing involves introducing a mixture of an inert gas such as argon or nitrogen with a reactive gas such as chlorine or sulfur hepa-fluoride into the molten aluminum to collect hydrogen and de-wet solid impurities. The gas mixture bubbles to the surface with the hydrogen and oxide impurities.
However, these materials are highly noxious and can cause harmful effluent bi-products. Improper use of these gasses creates environmental problems. Accordingly, there is significant governmental regulation. The proper storage, transport and use of these gasses is burdensome and expensive due to its harmful effects and the associated federal regulations.
Molten aluminum can also be subject to a flux degassing process. Flux degassing is the process of introducing a powdered or granulated salt mixture such as chloride and/or fluoride into the molten aluminum via a carrier gas such as nitrogen or argon. The salt flux can be introduced by a rotary degassing apparatus. An exemplary rotary apparatus includes a central hollow shaft attached to a rotor inserted into a pool of molten aluminum and rotated such that the salt flux travels down the hollow shaft and is dispersed within the molten aluminum through apertures in the rotor.
There remains a need to provide an apparatus and method to efficiently and safely handle the injection of a predetermined amount of degassing flux into the molten metal.